is enriched for heavy smokers, data from BigSib, a general community sample ascertained from the Australian Twin Registry on the basis of large sibship size [see (Saccone et al. 2007) for more information] were used to generate scoring coefficients more representative of the general population. An option in the Factor Procedure of SAS (SAS Institute 2004) enabled separate scoring coefficients to be calculated for women and men using BigSib sample data. The SAS Score Procedure was then used to apply these scoring coefficients to data from NAG project participants to obtain factor scores. Consistently high factor loadings for all component items were found for women (0.68-0.85) and men (0.63-0.92).
